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This command gives you the number of lines of every file in the folder and its subfolders matching the search options specified in the find command. It also gives the total amount of lines of these files.

The combination of print0 and files0-from options makes the whole command simple and efficient.

I use this (well I normally just drop the F=*.log bit and put that straight into the awk command) to count how many times I get referred from another site. I know its rough, its to give me an idea where any posts I make are ending up. The reason I do the Q="query" bit is because I often want to check another domain quickly and its quick to use CTRL+A to jump to the start and then CTRL+F to move forward the 3 steps to change the grep query. (I find this easier than moving backwards because if you group a lot of domains with the pipe your command line can get quite messy so its normally easier to have it all at the front so you just have to edit it & hit enter).

For people new to the shell it does the following. The Q and F equals bits just make names we can refer to. The awk -F\" '{print $4}' $F reads the file specified by $F and splits it up using double-quotes. It prints out the fourth column for egrep to work on. The 4th column in the log is the referer domain. egrep then matches our query against this list from awk. Finally wc -l gives us the total number of lines (i.e. matches).

One of the many things it regularily checks for is world writeable files.

If any are found, it writes the list to /var/log/security/writable.today.

"wc -l" simply counts the number of lines in the file.

This number should be low.

Browse through /var/log/security/writable.today and consider if any of those files *need* to be world-writeable (and if not, modify the permissions. eg: "chmod o-w $file").

A large number of world-writeable files may indicate that umask is not correctly set in /etc/profile (or ${HOME}/.bash_profile) but could also indicate poor security configuration or even malicious activity.

Upgraded Debian/Ubuntu/etc. systems may have a number of "orphaned" packages which are just taking up space, which can be found with the "deborphan" command. While you could just do "dpkg --purge $(deborphan)", the act of purging orphans will often create more orphans. This command will get them all in one shot.